Ultrathin Metal–Organic Framework Nanosheet-Derived Ultrathin Co3O4 Nanomeshes with Robust Oxygen-Evolving Performance and Asymmetric Supercapacitors

Ultrathin metal-organic framework (MOF) nanosheets possessing inherent advantages of both two-dimensional (2D) features and MOFs are attracting intensive research interest. The direct manufacture of MOF nanosheets is still a challenge up to now. Here, we have developed a novel bottom-up approach to synthesize zeolitic imidazolate framework-67 (ZIF-67) nanosheets, which can be in situ converted into Co3O4 ultrathin nanomeshes after thermal treatment. Interestingly, the obtained Co3O4 nanomeshes are rich in oxygen defects, providing fruitful active sites for the faradaic reaction. The modified electrode exhibits a large specific capacitance (1216.4 F g-1 at 1 A g-1), as well as a high rate capability (925.5 F g-1 at 20 A g-1). Moreover, an asymmetric supercapacitor made of Co3O4//activated carbon shows an energy density of 46.5 Wh kg-1 at 790.7 W kg-1. Furthermore, the 2D Co3O4 ultrathin nanomeshes show an outstanding performance for the oxygen evolution reaction with an overpotential of 230 mV at the onset potential and a small Tafel slope of 74.0 mV dec-1. The present method presents a facile avenue to the preparation of other 2D ultrathin metal oxide nanostructures with various applications in energy catalysis and conversion.